LRUCache実装

私が書いたLRUCacheの実現

import java.util.Hashtable;


public class LRUCache {
    class CacheNode {
        CacheNode prev;
        CacheNode next;
        Object key;
        Object value;
    }

    private int cacheSize;
    private int currentSize;
    private Hashtable<Object,CacheNode> nodes;
    private CacheNode first;
    private CacheNode last;

    public LRUCache(){}

    public LRUCache(int size){
        this.cacheSize = size;
        this.nodes = new Hashtable<Object,CacheNode>(size);
        this.currentSize = 0;
    }

    public void moveToHead(CacheNode node){
        if(first == node){
            return;
        }
        if(node.prev != null){
            node.prev = node.prev.next;
        }

        if(node.next != null){
            node.next.prev = node.prev;
        }

        if(last == node){
            last = node.prev;
        }

        if(first != null){
            first.prev = node;
            node.next = first;
        }

        first = node;
        node.prev = null;
        if(last == null){
            last = first;
        }
    }

    public void removeLast(){
        if(last != null){
            if(last.prev != null){
                last.prev.next = null;
            } else {
                first = null;
            }
            last = last.prev;
            nodes.remove(last.key);
            currentSize--;
        }
    }

    public void put(Object key, Object value){
        CacheNode node = nodes.get(key);
        if(node == null){
            if(currentSize >= cacheSize){
                if(last != null){
                    nodes.remove(key);
                }
                removeLast();
            } else {
                currentSize++;
            }
            node = new CacheNode();
        }
        node.key = key;
        node.value = value;
        moveToHead(node);
        nodes.put(key, node);
    }

    public Object get(Object key){
        CacheNode node = nodes.get(key);
        if(node != null){
            moveToHead(node);
            return node.value ;
        }
        return null;
    }

    public Object remove(Object key){
        CacheNode node = nodes.get(key);
        if(node != null){
            if(node.prev != null){
                node.prev.next = node.next;
            } else {
                first = null;
            }

            if(node.next != null){
                node.next.prev = node.prev;
            }

            if(first == node){
                first = node.next;
            }

            if(last == node){
                last = node.prev;
            }

            nodes.remove(key);
            currentSize--;
            return node.value;
        }
        return null;
    }
}